Polymer fuse and filter apparatus

ABSTRACT

A fuse and filter arrangement having a polymer fuse apparatus that provides bypass fuse protection. A polymer bypass fuse includes of an electrical conductor wherein a portion of the conductor is surrounded by an internal electrode, which is then surrounded by a layer of polymeric positive temperature coefficient (PTC) material, which is then surrounded by a conductive material similar to that of the internal electrode.  
     The fuse and filter arrangement includes a plurality of in-line and bypass fuses combined with a differential and common mode filter, which itself consists of a plurality of common ground conductive plates maintaining first and second electrode plates between the various conductive plates, all of which are surrounded by a material having predetermined electrical characteristics to provide fail safe filter and circuit protection.

[0001] This application is a continuation of co-pending application Ser.No. 10/142,026 filed May 9, 2002, which is a continuation of applicationSer. No. 09/939,547 filed Aug. 24, 2001, now issued as U.S. Pat. No.6,388,856, which is a continuation of application Ser. No. 09/583,831filed May 31, 2000, now issued as U.S. Pat. No. 6,282,074, which is adivisional of application Ser. No. 09/238,312 filed Jan. 28, 1999, nowissued as U.S. Pat. No. 6,157,528. Application Ser. Nos. 09/238,312,09/583,831, 09/939,547, and 10/142,026 are hereby incorporated byreference.

TECHNICAL FIELD

[0002] The present invention relates to polymeric positive temperaturecoefficient (PTC) over current protection devices and more specificallywith a polymeric over current protection device an in-line and/or bypassfuse which can also be within a self contained component which combinesa plurality of in-line and/or bypass fuses with additional electroniccircuitry.

BACKGROUND OF THE INVENTION

[0003] Abnormally high currents or over currents have the potential todestroy electrical circuitry and equipment plus become a safety/shockhazard to people. For years electrical equipment has been protectedthrough the use of fuses or circuit breakers. The typical fuse has aninternal by-metallic conductor through which current passes. If thecurrent through the system exceeds the rated value of the fuse, theby-metallic conductor will begin to melt. If the over current continues,eventually the by-metallic conductor will melt through thereby breakingthe current path between the supply and the load. Circuit breakers breakthe current path between the power source and the load just as the fuseexcept that in the case of the circuit breaker an electromagnet in thedevice draws a connecting metallic link out of the circuit when currentlevels exceed rated conditions thereby opening the current path.

[0004] While typical fuses are effective in protecting electricalequipment they must be replaced once the by-metallic conductor hasmelted thereby proving not to be cost effective, both with regard toreplacement and maintenance costs. Circuit breakers on the other handare reusable but are typically more expensive than fuses and stillrequire user intervention to reset them once an over current has beencorrected.

[0005] An improvement over by-metallic fuses and circuit breakers is thepolymeric (positive temperature coefficient) PTC device which protectscircuits by going from a low to a high resistance state in response toan over current. Polymeric PTC devices respond to over currents byincreasing their resistance as the device's temperature increases due tothe generation of heat within the device from power dissipation. Theadvantage these devices provide is that once the over current conditionhas been corrected and the devices temperature decreases to its normaloperating point, its resistance will decrease in effect resetting thedevice. Polymeric PTC devices provide the compact dimensions provided byfuses with the ability to be reused as provided by circuit breakers.These devices have the added advantage of being automatically reset oncenormal operating conditions in a circuit are restored.

[0006] To date, polymeric PTC devices have been manufactured in standardelectronic packaging, similar to a disk capacitor, in which thepolymeric material is encapsulated in a disk shaped enclosure with twowire leads extending therefrom. This type of packaging is designed forthrough hole circuit board mounting. While this configuration protectscircuitry from over current conditions, the through hole wire leads andassociated copper tracks and wiring used to connect the polymer PTCdevices cause another problem, that being radiated emissions ofelectromagnetic noise.

[0007] The wire leads and copper tracks used by the polymeric PTCdevices are effected by two different types of conductive currents,differential mode and common mode. The fields generated by thesecurrents create the radiated emissions. Differential mode currents arecurrents which flow in a circular path in wires, copper traces, andother conductors such that the fields associated with these currentsoriginates from the loop defined by the conductors. Such a circuit isessentially a loop antenna with the resulting field being primarilymagnetic. Differential mode emissions are typically found at frequenciesbelow 1 MHz.

[0008] Common mode currents are completely different in nature fromdifferential mode currents in that they flow in a different circuit pathand dominate at higher frequencies, those typically above 1 MHz. Commonmode currents typically return to their source through parasiticcapacitance inherently found in electronic circuits. To minimize commonmode currents between lines, an alternate low impedance return path forthese currents must be provided while increasing the impedance of thecommon mode current path.

[0009] A major drawback to differential and common mode filters of theprior art is that if capacitors failed they would adversely affect thecircuitry they were originally used to filter or protect. Dependent uponthe application, this condition would also present a safety hazard tohumans. To overcome this problem numerous fuses had to be employed invarious configurations to ensure the electrical conductors to befiltered were protected from both the filter and other circuitry.Despite the numerous fuses and inconvenience of using so many fuses, inmany applications it was absolutely necessary to prevent inconvenienceor even life threatening conditions. One example is the use of filtersin the automotive industry. When used to filter differential and commonmode electrical noise from conductors in power steering or power brakes,filtering improves the overall operation but is not critical to thisoperation but if the filter failed and destroyed surrounding othercircuitry, the brake or power steering systems could become disabledeither stranding or endangering the driver if failure occurred while thevehicle was moving. Because of this it is critical that any filters usedbe self protecting in that they effectively remove themselves fromcircuitry they were originally intended to protect upon their failure.

[0010] As a result, one object of the present invention is to providein-line and/or bypass fuse protection in a single, compact electricaldevice which allows defective circuitry to disconnect or remove itselffrom protected circuitry while not presenting a safety hazard.

[0011] It is a further object of the present invention to provide acompact hybrid device which combines various types of filter and surgeprotection with in-line and/or bypass fuse protection to improve overallcircuit performance and insure that under extreme conditions partialcircuit failure does not damage additional circuitry.

[0012] It is an additional object of the present invention to provide afilter apparatus capable of removing itself from additional circuitryupon its own failure such that continued operation of the overall systemcan be maintained in spite of the filter's failure thereby providingadditional safety when used in conjunction with systems whose failurecan endanger human life.

[0013] Therefore, in light of the foregoing deficiencies in the priorart, Applicant's invention is herein presented.

SUMMARY OF THE INVENTION

[0014] The present invention relates to a polymer fuse apparatus thatprovides bypass fuse protection. A polymer bypass fuse is comprised ofan electrical conductor wherein a portion of the conductor is surroundedby an internal electrode, which is then surrounded by a layer ofpolymeric positive temperature coefficient (PTC) material, which is thensurrounded by a conductive material similar to that of the internalelectrode.

[0015] During normal operation the polymeric PTC material is in aconductive state thereby allowing electrical coupling between theconductor and the outer conductive material or contact electrode. If thecurrent through the polymeric PTC material increases beyond acceptablelimits, the polymeric PTC material will become highly resistive therebycreating an open condition which prevents conduction. Various hybridcombinations are also contemplated where in-line and/or bypass fuses arecombined with other circuit components. One example is, a plurality ofin-line and bypass fuses combined with a differential and common modefilter, which itself consists of a plurality of common ground conductiveplates maintaining first and second electrode plates between the variousconductive plates, all of which are surrounded by a material havingpredetermined electrical characteristics to provide filter and circuitprotection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 shows the polymer fuse of the present invention whereinFIG. 1a is a front elevational view in cross section, FIG. 1b is a topplan view of the same and FIG. 1c is a schematic representation of thesame;

[0017]FIG. 2 is a graph depicting the operating curve for the polymericPTC material in the polymer bypass fuse of FIG. 1;

[0018]FIG. 3 is a front elevational view in cross section of a hybridpolymer bypass fuse having additional electronic components;

[0019]FIG. 4 is a schematic representation of the assembly of FIG. 3wherein the additional electronic component is a varistor;

[0020]FIG. 5 is a schematic representation of the assembly of FIG. 3wherein the additional electronic component is a capacitor;

[0021]FIG. 6 is a perspective view of a line filter which employs thepolymer bypass fuse shown generally in FIG. 1;

[0022]FIG. 7 is a schematic representation of the line filter depictedin FIG. 6 designed for over current protection;

[0023]FIG. 8 is a schematic representation of the line filter depictedin FIG. 6 designed to suppress electromagnetic from to differential andcommon mode currents;

[0024]FIG. 9 is an exploded front elevational view in cross section ofan in-line and bypass fuse;

[0025]FIG. 10 is a front elevational view in cross section of thein-line and bypass fuse of FIG. 9;

[0026]FIG. 11 is a schematic diagram which represents electrically thein-line and bypass fuse shown in FIGS. 9 and 10;

[0027]FIG. 12 is an exploded perspective view of a plurality of in-lineand bypass fuses as shown in FIGS. 9 through 11 incorporated within afilter to create a hybrid differential and common mode filter within-line and bypass fuse protection;

[0028]FIG. 13 is a schematic representation of the electricalcharacteristics of the hybrid component shown in FIG. 12;

[0029]FIG. 14 shows an exploded perspective view of a differential andcommon mode filter similar to that shown in FIG. 12;

[0030]FIG. 15 provides a schematic diagram of the filter shown in FIG.14;

[0031]FIG. 16 provides a schematic representation of the physicalarchitecture of the filter shown in FIG. 14;

[0032]FIG. 17 is an exploded perspective view of the differential andcommon mode filter having in-line and bypass fuse protection; and

[0033]FIG. 18 is a perspective view in cross-section of the differentialand common mode filter having in-line and bypass fuse protection asshown in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034]FIG. 1 shows polymer bypass fuse 10 which is comprised ofelectrical conductor 18 wherein a portion of conductor 18 is surroundedby internal electrode 16 which is essentially a conductive material suchas metal like copper. Electrode 16 is then surrounded by a layer ofpolymeric positive temperature coefficient (PTC) material 14, which isthen itself surrounded by a conductive material, similar to that ofinternal electrode 16, which makes up contact electrode 12. FIG. 1bshows the circular relationship between conductor 18, internal electrode16, polymeric PTC material 14 and contact electrode 12. While notcrucial, it is best that each of the layers be uniform so that theradius from conductor 18 to the outer edge of contact electrode 12 isconstant in all directions. FIG. 1c is a schematic representation ofbypass fuse 10 as shown in FIGS. 1a and 1 b. Feed through conductor 20represents conductor 18 with connection points 22 on either end ofconductor 20 being coupling points used to interface bypass fuse 10 withexternal circuitry. PTC device 24 is coupled on one end with conductor20 with component interface point 26 on the other. PTC device 24represents polymeric PTC material 14 and component interface point 26represents contact electrode 12.

[0035] In operation, bypass fuse 10 is coupled in series with anexternal electronic circuit such that a signal path, for instance apower supply connection, is connected to conductor 18 to supply powerthrough bypass fuse 10. Because internal electrode 16 is conductive andcoupled to conductor 18, current traveling through conductor 18 willalso travel through internal electrode 16. At normal temperatures, PTCmaterial 14 conducts electricity due to its normally low resistancethereby providing a path from conductor 18 to contact electrode 12.External circuitry can then be coupled to contact electrode 12 and besupplied with current from conductor 18. This would be one method ofcoupling a circuit to a power supply so that if the circuit shorted outcurrent could be maintained to other circuits tied to the same supply.Bypass fuse 10 provides this type of protection in that if circuitcoupled to contact electrode 12 begins to draw high levels of current,the internal temperature of bypass fuse 10 will increase therebyincreasing the temperature of PTC material 14 making it highlyresistive. If the temperature reaches a predetermined trip point PTCmaterial 14 will become substantially non-conductive. The advantageprovided by bypass fuse 10 is that current flow through conductor 18 isunaffected by the defective circuit which has now been disconnected fromconductor 18 due to the high resistive state of PTC material 14.

[0036]FIG. 2 shows a graph depicting the operating curve for PTCmaterial 14. PTC material 14, for all practical purposes, has noresistance in temperatures up to approximately 80° C. Once at 80° C.,onset temperature 30 is reached and PTC material 14 begins to changefrom its normal crystalline state to an amorphous state where itsresistance begins to increase. As PTC material 14 continues to increasein temperature it enters polymeric expansion area 32 where it slowlyincreases in resistance in almost a linear fashion as the temperatureincreases. At approximately 140° C. current flow interrupt temperature34 is reached at which PTC point material 14 is primarily resistivethereby preventing most current flow between internal electrode 16 andcontact electrode 12. As the temperature continues to increase, PTCmaterial 14 will increase in resistance by five decades at point 36 andthen finally reach its peak resistance temperature 38 at approximately170° C. Once PTC material 14 reaches point 36, substantially no currentis flowing through material 14.

[0037]FIG. 3 shows hybrid bypass fuse 50 which incorporates a polymericPTC bypass fuse with additional electronic components. The physicalembodiment of bypass fuse 50 in FIG. 3 is shown in cross section and isrepresented schematically by FIG. 4 or FIG. 5, depending upon the makeupof material 58. FIG. 3 is similar to the embodiment shown in FIG. 1 withthe addition of material 58 and insulation 62. As described earlier,conductor 56 passes through bypass fuse 50 and is electrically coupledto internal electrode 54. PTC material 60 then surrounds a portion ofinternal electrode 54 with PTC material 60 itself surrounded bydielectric material 58. Depending on its makeup, material 58 when usedwith internal electrode 54 and contact electrode 52, forms either avaristor 76 as shown in FIG. 4 or a capacitor 82 as shown in FIG. 5 isformed in series with PTC device 74. To further protect bypass fuse 50from damage and its surrounding environment, insulation 62 is added toseal PTC material 60 and material 58 within contact electrode 52.Insulation 62 also maintains electrical isolation between contactelectrode 52 and conductor 56.

[0038] As described for FIG. 1, PTC material 60, when operated undernormal conditions, allows conduction from conductor 56, through internalelectrode 54 to material 58, internal electrode 54 and contact electrode52, as shown in FIG. 3, act as parallel plates separated only bymaterial 58 and PTC material 60. If material 58 is a material as foundin capacitors then FIG. 5 schematically represents the embodiment shownin FIG. 3 consisting of PTC device 74 coupled in series with capacitor82, together coupled from feed through conductor 70 to connection point78. If material 58 is a metal oxide or MOV-type material then theconfiguration shown in FIG. 4 is representative consisting of PTC device74 coupled in series with varistor 76 together coupled from feed throughconductor 70 to connection point 78. In both FIGS. 4 and 5, feed throughconductor 70 having feed through connection points 72 on either endrepresents conductor 56. PTC device 74 represents material 60 whichcomes in physical contact with internal electrode 54 and material 58.The embodiment shown in FIG. 3 is a simple configuration that allowscurrent to flow through conductor 56 and at the same time allows forcoupling of components to conductor 56 through fuses. This preventsconductor 56 from being loaded down under abnormal operating conditionsby breaking the electrical connection of additional components whilebeing able to reset automatically once faulty conditions are corrected.

[0039]FIG. 6 shows bypass fused line-to-line filter 90 which makes up aline conditioning device which incorporates two polymer bypass fuses 10with either differential and common mode filter/over current protectiondevice 94 or differential and common mode filter 96, as shown in FIGS. 7and 8. Both differential and common mode filter/over current protectiondevice 94 and differential and common mode filter 96 are described inrelation to FIGS. 14 through 16 and in Applicant's currently pendingapplication Ser. No. 08/841,940 filed on Apr. 8, 1997 which isincorporated herein by reference. If either configuration 94 or 96shorts or fails causing abnormal current draw, PTC devices 24 willincrease in resistance until configurations 94 or 96 are disconnectedfrom feed through conductors 20 so that other circuitry coupled to feedthrough conductors 20 is unaffected by the faulty components. If at anytime the malfunction is corrected, current draw through bypass fuse 10will decrease thereby decreasing the temperature of PTC device 24. Asthe temperature returns to normal bypass fuse 10 will become conductiveand circuit configurations 94 or 96 will once again be coupled to feedthrough conductors 20.

[0040]FIGS. 9, 10 and 11 disclose a further embodiment of the presentinvention which provides both in-line and bypass fuse protection.Beginning with FIG. 11, a schematic representation of in-line and bypassfuse 100, bypass connection 106 is electrically coupled in series withPTC device 108 which is then coupled to feed through terminationconductor 110. In-line connection 104 is directly coupled to feedthrough termination conductor 110 which is coupled to PTC devices 114and 108. Such a configuration allows, for example, a power supply to becoupled to in-line connection 104 to provide power through in-lineconnection 102 for external circuitry. Bypass connection 106 allowsadditional circuitry to be tied off of the same power supply. Theconfiguration shown in FIG. 11 provides for total protection in thatcurrent overloads, whether coupled in series or in parallel with acircuit connected to in-line connection 104 are now provided withautomatically resettable fuse protection.

[0041] In-line and bypass 100, in both FIGS. 9 and 10, is shown in crosssection and, as in the embodiment of FIG. 1, is preferred to be circularin shape. Describing the device vertically from top to bottom, in FIG.10, bypass connection 106 is coupled to outer casing or termination band124 which is a conductive metallic surface encircling the outercircumference of in-line and bypass fuse 100. Bypass connection 106 isoptional as external circuitry could be coupled directly to conductivetermination band or casing 124 with the same effect. Within outertermination band 124 is contact electrode 110 having a U-shaped cavitywhich maintains a barrier between outer casing 124 and inner area 126.PTC material 112 is maintained between and separates outer terminationband 124 and contact electrode 110. In-line connection 102 is thencoupled to contact electrode 118 and disposed within inner area 126 withPTC material 116 covering contact electrode 118 thereby creating abarrier between contact electrode 118 and contact electrode 110. FIG. 10shows in-line and bypass fuse 100 in cross section fully assembled.Under normal operating conditions, power coupled to in-line connection102 will be made available at in-line connection 104 and bypassconnections 106 due to the normally conductive state of PTC materials112. When such material is normally conductive, in-line and bypass fuse100 is essentially a single electrical node.

[0042]FIG. 12 shows component 120 which is an embodiment of the presentinvention having both in-line and bypass fuse protection, as shown inFIGS. 9-11, combined with a differential and common mode filter.Component 120 is comprised of differential and common mode filter 122having a plurality of apertures 156 in which in-line and bypass fuses100 and 100′ are within. Each fuse 100 and 100′ includes first in-lineconnections 102 and 102′ and second in-line connections 104 and 104′which are conductors allowing feed through coupling of electricalsignals through the fuses. Fuse 100 and 100′ also include bypassconnection 106 and 106′.

[0043]FIG. 13 is a schematic representation of component 120, shown inFIG. 12, with differential and common mode filter 122 coupled to in-lineand bypass fuses 100 and 100′ wherein each fuse provides protectionbetween first and second in-line connections 102 and 104 and protectionbetween second in-line connection 104 and bypass connection 106. Theconfiguration shown in both FIGS. 12 and 13 allows differential andcommon mode filtering between two conductors while at the same timeproviding bypass protection if differential and common mode filter 122fails. Conduction between first and second in-line connections 102 and104 is not affected by failure of filter 122 and at the same timeprotection is provided for each conductive path due to in-line fuseprotection. The same relationships apply to in-line connections 102′ and104′ although not described. The configuration provides all the benefitsof differential and common mode filtering while providing its ownfailsafe, protection i.e., if the filter fails it takes itselfcompletely out of the circuit allowing for continued operation of theexternal circuitry coupled to the filter with the only consequence beingthe elimination of the differential and common mode filtering. This typeof protection is necessary in applications in which filtering isdesirable but not necessary and failure of the filtering otherwise woulddisable the application all together. An example of this is in theautomotive industry. Automobiles today increasingly rely uponelectronics and microcomputer control of everything from engineperformance to stereo systems to power windows and locks. Because of theincreased amount of electronics within automobiles, the need fordifferential and common mode filtering has increased exponentially overthe years. In the past, if the filter failed the potential for anoverall short circuit existed which in some cases would completelydisable the vehicle leaving the driver stranded. Because of this obviousdrawback, the need for filter protection with the ability to removeitself from its host upon failure is extremely desirable. Not only coulda driver or user be left stranded but electrical failure duringoperation could cause other systems to fail such as power steering orpower brakes thereby placing the user in extreme danger. Of course,automobiles are not the only use for the present invention, all types ofelectronic circuits such as those used in airplanes, trains and heavyequipment all can benefit from the combination of differential andcommon mode filtering with in-line and bypass fuse protection.

[0044]FIG. 14 shows an exploded perspective view of the physicalarchitecture of differential and common mode filter 300. Differentialand common mode filter 300 is described fully in Applicant's currentlypending application Ser. No. 08/841,940, which has already beenincorporated by reference. Nevertheless, the filter will be describedherein in some detail. Filter 300 is comprised of a plurality of commonground conductive plates 304 at least two electrode plates 306 a and 306b where each electrode plate 306 is sandwiched between two common groundconductive plates 304. At least one pair of electrical conductors 302 aand 302 b is disposed through insulating apertures 308 or couplingapertures 310 of the plurality of common ground conductive plates 304and electrode plates 306 a and 306 b with electrical conductors 302 aand 302 b also being selectively connected to coupling apertures 310 ofelectrode plates 306 a and 306 b. Common ground conductive plates 304consist entirely of a conductive material such as metal in the preferredembodiment. At least one pair of insulating apertures 308 are disposedthrough each common ground conductive plate 304 to allow electricalconductors 302 to pass through while maintaining electrical isolationbetween common ground conductive plates 304 and electrical conductors302. The plurality of common ground conductive plates 304 may optionallybe equipped with fastening apertures 312 arranged in a predetermined andmatching position to enable each of the plurality of common groundconductive plates 304 to be coupled securely to one another throughstandard fastening means such as screws and bolts. Fastening apertures312 may also be used to secure differential and common mode filter 300to another surface such as an enclosure or chassis of the electronicdevice filter 300 is being used in conjunction with.

[0045] Electrode plates 306 a and 306 b are similar to common groundconductive plates 304 in that they are comprised of a conductivematerial and have electrical conductors 302 a and 302 b disposed throughapertures. Unlike common ground conductive plates 304, electrode plates306 a and 306 b are selectively electrically connected to one of the twoelectrical conductors 302. While electrode plates 306, as shown in FIG.14, are depicted as smaller than common ground conductive plates 304this is not required but in this configuration has been done to preventelectrode plates 306 from interfering with the physical coupling meansof fastening apertures 312.

[0046] Electrical conductors 302 provide a current path which flows inthe direction indicated by the arrows positioned at either end of theelectrical conductors 302 as shown in FIG. 14. Electrical conductor 302a represents an electrical signal conveyance path and electricalconductor 302 b represents the signal return path. While only one pairof electrical conductors 302 a and 302 b is shown, Applicantcontemplates differential and common mode filter 300 being configured toprovide filtering for a plurality of pairs of electrical conductorscreating a high density multi-conductor differential and common modefilter.

[0047] The final element which makes up differential and common modefilter 300 is material 318 which has one or a number of electricalproperties and surrounds the center common ground conductive plate 304,both electrode plates 306 a and 306 b and the portions of electricalconductors 302 a and 302 b passing between the two outer common groundconductive plates 304 in a manner which completely isolates all of theplates and conductors from one another except for the connection createdby the conductors 302 a and 302 b and coupling aperture 310. Theelectrical characteristics of differential and common mode filter 300are determined by the selection of material 318. If a dielectricmaterial is chosen filter 300 will have primarily capacitivecharacteristics. Material 318 may also be a metal oxide varistormaterial which will provide capacitive and surge protectioncharacteristics. Other materials such as ferrites and sinteredpolycrystalline may be used wherein ferrite materials provide aninherent inductance along with surge protection characteristics inaddition to the improved common mode noise cancellation that resultsfrom the mutual coupling cancellation effect. The sinteredpolycrystalline material provides conductive, dielectric, and magneticproperties. Sintered polycrystalline is described in detail in U.S. Pat.No. 5,500,629 which is herein incorporated by reference.

[0048] Still referring to FIG. 14, the physical relationship of commonground conductive plates 304, electrode plates 306 a and 306 b,electrical conductors 302 a and 302 b and material 318 will now bedescribed in more detail. The starting point is center common groundconductive plate 304. Center plate 304 has the pair of electricalconductors 302 disposed through their respective insulating apertures308 which maintain electrical isolation between common ground conductiveplate 304 and both electrical conductors 302 a and 302 b. On eitherside, both above and below, of center common ground conductive plate 304are electrode plates 306 a and 306 b each having the pair of electricalconductors 302 a and 302 b disposed there through. Unlike center commonground conductive plate 304, only one electrical conductor, 302 a or 302b, is isolated from each electrode plate, 306 a or 306 b, by aninsulating aperture 308. One of the pair of electrical conductors, 302 aor 302 b, is electrically coupled to the associated electrode plate 306a or 306 b respectively through coupling aperture 310. Coupling aperture310 interfaces with one of the pair of electrical conductors 302 througha standard connection such as a solder weld, a resistive fit or anyother method which will provide a solid and secure electricalconnection. For differential and common mode filter 300 to functionproperly, upper electrode plate 306 a must be electrically coupled tothe opposite electrical conductor 302 a than that to which lowerelectrode plate 306 b is electrically coupled, that being electricalconductor 302 b. Differential and common mode filter 300 optionallycomprises a plurality of outer common ground conductive plates 304.These outer common ground conductive plates 304 provide a significantlylarger ground plane which helps with attenuation of radiatedelectromagnetic emissions and provides a greater surface area in whichto dissipate over voltages and surges. This is particularly true whenplurality of common ground conductive plates 304 are not electricallycoupled to circuit or earth ground but are relied upon to provide aninherent ground. As mentioned earlier, inserted and maintained betweencommon ground conductive plates 304 and both electrode plates 306 a and306 b is material 318 which can be one or more of a plurality ofmaterials having different electrical characteristics.

[0049]FIG. 15 is a schematic representation demonstrating that filter300 provides a line-to-line capacitor 320 between and coupled toelectrical conductors 302 a and 302 b and two line-to-ground capacitors322 each coupled between one of the pair of the electrical conductors302 and inherent ground 324. Also shown in dashed lines is inductance326 which is provided if material 318 is comprised of a ferritematerial, as described in more detail later.

[0050]FIG. 16 shows a quasi-schematic of the physical embodiment offilter 300 and how it correlates with the capacitive components shown inFIG. 15. Line-to-line capacitor 320 is comprised of electrode plates 306a and 306 b where electrode plate 306 a is coupled to one of the pair ofelectrical conductors 302 a with the other electrode plate 306 b beingcoupled to the opposite electrical conductor 302 b and separated bycommon ground plate 304 thereby providing the parallel plates necessaryto form two capacitors in series. Center common ground conductive plate304 acts as inherent ground 324 and also serves as one of the twoparallel plates for each line-to-ground capacitor 322.

[0051] The second parallel plate required for each line-to-groundcapacitor 322 is supplied by the corresponding electrode plate 306. Bycarefully referencing FIG. 14 and FIG. 16, the capacitive platerelationships will become apparent. By isolating center common groundconductive plate 304 from each electrode plate 306 a or 306 b withmaterial 318 having electrical properties, the result is a capacitivenetwork having a common mode bypass capacitor 320 extending betweenelectrical conductors 302 a and 302 b and line-to-ground decouplingcapacitors 322 coupled from each electric al conductor 302 a and 302 bto inherent ground 324.

[0052] Inherent ground 324 will be described in more detail later butfor the time being it may be more intuitive to assume that it isequivalent to earth or circuit ground. To couple inherent ground 324,which center and additional common ground conductive plates 304 form,one or more of common ground conductive plates 304 are coupled tocircuit or earth ground by common means such as a soldering or mountingscrews inserted through fastening apertures 312 which are then coupledto an enclosure or grounded chassis of an electrical device. Whiledifferential and common mode filter 300 works equally well with inherentground 324 coupled to earth or circuit ground, one advantage of physicalarchitecture of is filter 300 that a physical grounding connection isunnecessary.

[0053] Referring again to FIG. 14, an additional feature of differentialand common mode filter 300 is demonstrated by clockwise andcounterclockwise flux fields, 314 and 316 respectively. The direction ofthe individual flux fields is determined and may be mapped by applyingAmpere's Law and using the right hand rule. In doing so an individualplaces their thumb parallel to and pointed in the direction of currentflow through electrical conductors 302 a or 302 b as indicated by thearrows at either ends of the conductors. Once the thumb is pointed inthe same direction as the current flow, the direction in which theremaining fingers on the person's hand curve indicates the direction ofrotation for the flux fields. Because electrical conductors 302 a and302 b are positioned next to one another and represent a single currentloop as found in many I/O and data line configurations, the currentsentering and leaving differential and common mode filter 300 are opposedthereby creating opposed flux fields which cancel each other andminimize inductance. Low inductance is advantageous in modern I/O andhigh speed data lines as the increased switching speeds and fast pulserise times of modern equipment create unacceptable voltage spikes whichcan only be managed by low inductance surge devices. When used as afilter the low inductance results in a high self resonant frequencywhich is desirable in high speed data lines and other high frequencyapplications.

[0054]FIG. 17 is a more detailed view of the apparatus shown in FIGS. 12and 13. Differential and common mode filter 130, which is similar to thefilter described in detail in FIGS. 14, 15, and 16, is comprised ofcommon ground conductive plates 132, 136 and 140 with first and secondelectrode plates 134 and 138 coupled to the common ground conductiveplates so that each electrode plate is maintained between two commonground conductive plates. Although not shown in FIG. 17, FIG. 18 showsthat each common ground conductive plate and electrode plate includes aplurality of apertures 156 in which in-line and bypass fuses 100 and100′ are disposed within and then coupled to differential and commonmode filter 130. As shown in FIG. 17, in-line and bypass fuse 100includes insulating surface 146 and bypass connection 144 whereininsulating surface 146 prevents all but a predetermined plate from beingelectrically coupled to first and second in-line connections 102 and104. Once fuse 100 is disposed within the selected aperture ofdifferential and common mode filter 130, bypass connection 144 will beelectrically coupled to second electrode plate 138. Fuse 100′ isidentical to fuse 100 but is inserted within a predetermined aperture offilter 130 in the opposite direction as that of fail open fuse 100 sothat bypass connection 144′ will be electrically coupled to firstelectrode plate 134.

[0055] This arrangement will now be described in more detail withreference to FIG. 18 which shows filter 130 in cross section.Differential and common mode filter 130 is comprised of common groundconductive plates 132, 136 and 140 with first electrode plate 134maintained between the two common ground conductive plates 132 and 136and second electrode plate 138 maintained between common groundconductive plates 136 and 140. While the numerous plates are maintainedadjacent each other they do not actually come in contact with oneanother but instead are surrounded by material 152 having predeterminedelectrical properties as described earlier. The outer edges of eachcommon ground conductive plate are coupled to common ground 154 whichelectrically connects each of the common ground conductive plates to oneanother. Common ground 154 allows for a more distributed inherent groundfor filter 130. Inline and bypass fuse 100 is disposed within filter 130through aperture 156. Although not shown, bypass connection 144 ofin-line and bypass fuse 100 is electrically coupled to first electrodeplate 134 by coupling 150. Coupling 150 is used in various places andmay consist of any material that will maintain electric and physicalcoupling between two conductive surfaces. In the preferred embodimentcoupling 150 is a type of solder or weld. Fuse 100′ is also disposedwithin filter 130 through an aperture 156 such that bypass connection144′, not shown, is electrically coupled to second electrode plate 138via a coupling 150. An alternate approach to interconnecting the commonground plates consists of using conductive rod 158 disposed withinfilter 130 to provide a means of connecting a true ground to the variouscommon ground conductive plates. As shown in FIG. 18, coupling 150 isused to electrically connect conductive rod 158 to each of the commonground conductive plates 132, 136 and 140. Again not shown, in-line andbypass fuses 100 and 100′ could consist entirely of a conductive surfaceas opposed to having bypass connection 144 and insulating surface 146.In this type of configuration the individual common ground conductiveplates and unwanted electrode plate would have insulation withinapertures 156 thereby only allowing electrical coupling between thedesired fuse and a predetermined electrode or common ground conductiveplate. In this alternate embodiment, in-line and bypass fuse 100 and100′ would be identical and could be inserted within differential andcommon mode filter 130 in the same direction or orientation as opposedto opposite directions from one another. Although the principals,preferred embodiments and preferred operation of the present inventionhave been described in detail herein, this is not to be construed asbeing limited to the particular illustrative forms disclosed. It willthus become apparent to those skilled in the art that variousmodifications of the preferred embodiments herein can be made withoutdeparting from the spirit or scope of the invention as defined by theappended claims.

What is claimed is:
 1. A device comprising; a first electrode definingat least the following elements, (1) upper plate, (2) a center plate,and (3) a lower plate, and wherein said upper plate is above said centerplate and said center plate is above said lower plate; a secondelectrode defining at least a second electrode plate, and wherein saidsecond electrode plate is below said upper plate and above said centerplate; a third electrode defining at least a third electrode plate, andwherein said third electrode plate is below said center plate and abovesaid lower plate; wherein said first electrode, said second electrode,and said third electrode, are each conductively isolated from oneanother; a plurality of fuses including a first fuse and a second fuse;wherein said first fuse is conductively coupled to said first electrode,and wherein said second fuse is conductively coupled to said thirdelectrode; and wherein said second electrode, said third electrode, andsaid center plate are positioned such that a line passing through saidsecond electrode and said third electrode contacts said center plate. 2.The device of claim 1, further comprising a ceramic dielectric, andwherein said ceramic dielectric is at least maintained between saidfirst, said second and said third electrode.
 3. The device of claim 1,further comprising a dielectric, and wherein said dielectric is at leastmaintained between any said plate of said device.
 4. The device of claim2 practicable for providing at least a line-to-line capacitor and twoline-to-ground capacitors to a circuit.
 5. The device of claim 3practicable for providing at least a line-to-line capacitor and twoline-to-ground capacitors to a circuit.
 6. The device of claim 1,further comprising a material, and wherein said material is at leastmaintained between any said plate of said device; and wherein saidmaterial is a material having either predominate ferrite properties, orpredominate varistor properties.
 7. The device of claim 5, wherein atleast said upper plate, said center plate, and said lower plate are ofsubstantially the same size; wherein said second electrode plate andsaid third electrode plate are of substantially the same size; andwherein at least said second electrode plate and said third electrodeplate are each smaller than either said upper plate, said center plate,or said lower plate.
 8. A device comprising; a first and a second fuseconductively isolated from each other; a first and a second electrode; ashielding electrode, and wherein said shielding electrode is arrangedbetween said first and said second electrode; wherein said first fuse isconductively coupled to said first electrode; wherein said second fuseis conductively coupled to said second electrode; wherein said shieldingelectrode, said first electrode, and said second electrode are eachconductively isolated from one another; and wherein a line passingthrough at least said first electrode to said second electrode contactssaid shielding electrode.
 9. The device of claim 8, further comprising amaterial practicable for spacing apart electrodes; and wherein saidmaterial is comprised of any one material or any combination ofmaterials taken from a group of materials consisting of a dielectricmaterial, a ferromagnetic material, and a varistor material.
 10. Thedevice of claim 9, wherein said shielding electrode is larger than atleast said first electrode.
 11. The device of claim 8, practicable forproviding at least a line-to-line capacitor and two line-to-groundcapacitors to a circuit.
 12. The device of claim 11, wherein either saidfirst fuse or said second fuse comprise a PTC material.
 13. A method ofmaking a device comprising: providing at least a first and a second fusethat are conductively isolated from each other; providing at least afirst and a second electrode that are conductively isolated from eachother; providing at least a shield electrode, wherein said shieldelectrode is arranged between said first and said second electrodemaintaining electrical isolation from each said electrode; wherein saidfirst fuse is conductively coupled to said first electrode; wherein saidsecond fuse is conductively coupled to said second electrode; andwherein a line passing through said first electrode and said secondelectrode contacts said shield electrode.
 14. The method of making adevice of claim
 13. wherein said method results in an energy bypassdevice practicable for differential mode and common mode noise filteringbetween at least said first electrode and said second electrode whenenergized.
 15. The method of making a device of claim 13, wherein saidfirst electrode and said second electrode are of substantially the samesize and shape as one another.
 16. The method of making a device ofclaim 13, wherein said first electrode and said second electrode arearranged in opposite orientation relative to each other.
 17. The methodof making a device of claim 16, wherein said first electrode and saidsecond electrode are each smaller than said shielding electrode.
 18. Themethod of making a device of claim 13, wherein said first electrode andsaid second electrode are of substantially the same size and shape asone another; wherein said first electrode and said second electrode arearranged in opposite orientation device relative to each other; andwherein said first electrode and said second electrode are each smallerthan said shielding electrode.
 19. A method of transmitting a signalcomprising: providing at least a first and a second fuse that areconductively isolated from each other; providing at least a first and asecond electrode that are conductively isolated from each other;providing at least a shield electrode, wherein said shield electrode isarranged between said first and said second electrode maintainingelectrical isolation from each said electrode; wherein said first fuseis conductively coupled to said first electrode; wherein said secondfuse is conductively coupled to said second electrode; wherein animaginary straight line passing through said first electrode and saidsecond electrode always contacts said shield electrode; connecting saidfirst electrode and said second electrode in a circuit; connecting saidshield electrode to a conductive area, and wherein said conductive areais not directly connected to a energy source or a load; and transmittinga signal to at least said second electrode.
 20. The method oftransmitting a signal of claim 19 practicable for providing at least aline-to-line capacitor and two line-to-ground capacitors to saidcircuit.